Thin Layer Multicycle Cathodic-Anodic Chronoamperometry of Atomic Hydrogen Injection–Extraction into Metals with Regard to the Stage of Phase Boundary Exchange

The method of potentiostatic anodic-cathodic chronoamperometry of atomic hydrogen injection into a metal film and its subsequent extraction is theoretically discussed. By combining the methods for studying the phase-structure state and surface morphology with multicycle cathodic-anodic chronoamperometry, the injection (and subsequent extraction) of atomic hydrogen into a 47Pd53Cu (at %) film synthesized by ion-plasma spraying is studied. It is found that the initial stage of hydrogenation proceeds under the mixed diffusion-phase-boundary control and passes to the purely diffusion control in 3–4 s. The main kinetic parameters of the stages of phase-boundary hydrogen penetration and its solid-phase diffusion are found. It is shown that the mass transfer in the film alloy proceeds mainly through the grain bodies rather than along intergrain boundaries. The increase in the β-phase content in the alloy leads to the noticeable increase in the diffusion coefficient of hydrogen, whereas the effective equilibrium constant of the phase-boundary process decreases.